For combustion engines with both a small fuel consumption and a small pollutant emission it is necessary to have a good knowledge about the characterization of a fuel spray atomized by an injection valve operating as a nozzle for producing a pulsed fuel spray. This holds both (a) for the spray characteristic of a direct injection valve which injects the fuel spray directly into a combustion volume of the combustion engine and (b) for the spray characteristic of an injection valve which is located at an intake tract of a combustion engine.
It is known to characterize the spatial distribution of a fuel spray by a grid of cells placed at a defined distance from the spray nozzle. The amount of fuel collected in each cell is weighted after a defined amount of time or injection events and the outcome is a 2d distribution of total flow. This kind of characterization has a strong limitation in accuracy limited by the cells' dimension and most importantly yields only a static characterization. It is impossible to measure the spatial characteristic of a fuel spray as a function of time. However, a corresponding measurement device allowing for a fuel spray characterization as a function of time would be highly welcome in particular in the field of combustion engine engineering, where highly dynamic application like fuel injectors are used.
DE 102011010461 A1 discloses a method for determining flow velocity in gaseous and liquid media. A heating resistor and a temperature dependent measurement resistor are provided in contact with the media. The heating resistor is supplied with a periodically changing voltage and the flow velocity is determined from a change of resistance of the measurement resistor.
DE 102007019927 B3 discloses an arrangement for measuring the velocity distribution in a measurement cross-section to examine liquid or gas flows. The arrangement uses and modifies a grating sensor in which the excitation electrodes and the receiver electrodes in each crossing point of the grid are electrically connected with each other through a solid body with a temperature-dependent resistor. Each excitation electrode is connected with a three-pole analogue switch to connect the electrodes selectively to a heating voltage source, a measurement voltage source or ground potential. Each receiver electrode is connected to an analog switch to connect the receiver electrode either to a fixed reference potential or to a current-voltage converter.